Process for the production of milk-product powders



United States Patent 3,410,701 PROCESS FOR THE PRODUCTION OFMILK-PRODUCT POWDERS Jacques Jean Ciboit, Paris, France, assignor toSociete Anonyme dite: Etablissements Laguilharre, Courbevoie,Hauts-de-Seine, France, a company of France No Drawing. Filed Feb. 23,1965, Ser. No. 434,617 Claims priority, application France, Feb. 21,1964, 964,641 3 Claims. (Cl. 99-203) ABSTRACT OF THE DISCLOSUREProduction of a milk-product concentrate containing more than 45% drysolids, at a temperature greater than 45 C., by spray-drying saidproduct to obtain a powder having a water content within the range of4.5 to 7%, an followed by subjecting the resulting powder to a differentsecondary drying treatment so as to reduce its water content toapproximately 3.5%.

This invention is directed to a process for the production ofmilk-product powders and also comprises, by way of novel industiralproducts, the powders which are obtained by means of said process. Theinvention is applicable especially, although not exclusively, to theproduction of powders of skimmed milk and the numerical values indicatedin the following description relate to this particular product.

It is known that, in conventional spray-drying processes in which thestarting material is a concentrate containing as a rule less than 45% ofdry product and in which a dry powder containing less than 4% water iscollected at the outlet of the spray chamber, the powders of the abovetype which are produced by these processes have satisfactory realsolubility. On the other hand, these powders have a high content ofoccluded air and low density. The presence of a high proportion ofoccluded air gives rise to a disadvantage in that troublesome foamformation results when dissolving the powder for the purpose ofreconstituting the milk. Furthermore, the low density of the saidpowders results in high total bulk of the containers in which they arepacked. This lastmentioned disadvantage becomes particularly marked whenthe powder which is produced by a conventional spray-drying process issubjected to a later moistening treatment or so-called instantaneizationtreatment which is intended to increase its wettability, the knowntreatments of this type having the effect of reducing even further thedensity of the powder.

It is an admitted fact that a number of means are already known forincreasing the density of a powder produced in a spray-drier and whichconsist either in increasing the percentage of dry material contained inthe initial concentrate, or in increasing the viscosity of the saidconcentrate, or in reducing the speed of rotation of the disc in thecasein which the spray atomization of the concentrate is efiected bymeans of a centrifugal disc, or in reducing the pressure in the case ofnozzles for spraying under pressure or with compressed air, oralternatively in modifying the inlet temperature of the drying air inthe spary chamber. It is also known, however, that all the meansreferred-to result in the production of powders which have poor realsolubility if the drying in the spray-drier is continued until a watercontent below 4% is reached. If the spray drying process is carried outunder these conditions, the powder retains poor real solubility evenafter an instantaneization treatment.

In addition, there have already been proposed a num- 3,410,701 PatentedNov. 12, 1968 p CC her of different processes for the production of skimmed-milk powder or lactoser-um in which a concentrate containing aproportion of dry material which is higher than 45 is subjected to aspray-drying process so performed as to collect at the outlet of thedrying chamber a powder having a high water content which can in certaincases be as high as 18%. These known processes, which aim to achievewithout any external addition of water the stabilization of the productby the more or less complete crystallization of the lactose contained inamorphous form in the starting concentrate, in fact require the presencein the powder of a free moisture content which is higher than 8%. Thisis essential in order to ensure crystallization, which takes place indifferent cases either within the drying chamber itself or within asecondary apparatus in which the powder extracted from the dryingchamber is maintained for a certain period of time in the presence ofthis moisture, the powder being subjected if desired. to a subsequentcomplementary drying operation. Processes of this kind are attended byserious operating difliculties by reason of the sticky nature of powderswhich have such a high moisture content and which adhere strongly to thewalls of the drying chamber, thereby calling for the utilization ofmechanical or compressed-air means for the purpose of detaching themtherefrom. In addition, this same moisture content has the effect ofproducing a certain degradtion of the proteins, thereby resulting in areduction in the real solubility of the powder. It has further beenobserved that powders in which the lactose has crystallized do not lendthemselves to a subsequent instantaneization treatment as readily asnormal spray-dried powders, in particular when it is desired to obtain apowder in the form of granules.

The process according to the present invention has for its object toelimniate the various drawbacks which have just been outlined by makingit possible to obtain milkproduct powders which have in particular thefollowing combination of properties:

(1) Contrary to the powders produced by conventional spray-dryingprocess, the lactose contained in the powders produced according to theinvention is practically unmodified or, in other words, has remained inan amorphous form;

(2) The said powders have a high density;

(3) They contain a small proportion of occluded air;

(4) They have excellent real solubility.

To this end, the process in accordance with the in vention consists inprinciple in subjecting to a spraydrying process a concentratecontaining a proportion of dry material which is higher than 45 andpreferably between 50 and and having a temperature which is higher than45 C. and preferably in the vicinity of to (3., by effecting the dryingin the spray-drier until a powder is obtained having a water contentwithin the range of 4.5 to 7% and preferably between 4.5 and 6%, .and inthen subjecting the powder thus obtained to a secondary drying operationso as to reduce its water content to approximately 3.5%.

Apart from the characteristic properties with which the powder isendowed as indicated earlier, it should be pointed out that, byoperating within the specified limits of water content at the outlet ofthe drying chamber, the process in accordance with the invention is notliable to result in the formation of any deposit on the chamber walls,thus considerably facilitating operating conditions with a view toachieving a continuous and steady manufacturing process on an industrialscale.

In the practical application of the invention, the spraydrying stagewill preferably be eifected in a drying tower fitted with a sprayingdevice consisting either of pressure nozzles or compressed-air nozzles.Good results can someture of the drying air in the spray-drier), Whileat the times also be obtained by making use of a spray device same timeretaining the other characteristic features of with centrifugal disc.the invention (temperature of injection of the concentrate The secondarydrying of the powder produced in the higher than 45 C. and preferably inthe vicinity of 60 spray-drier is preferably carried out immediatelyafter 5 65 C., water content of the powder at the outlet of theseparation of the powder from the drying air, and can drying chamberwithin the range of 4.5 to 7%, and secbe carried out by any suitablemeans, for example in a ondary drying of the powder). However, it wouldappear compressed-air system which is supplied with hot air or that,among the known means for increasing the density on a drying table. ofthe powder, the increase in concentration of the start- In all cases,the powder which has been subjected to the 10 ing concentrateconstitutes the most advantageous factor secondary drying process can besubjected if necessary to in the practical application of the inventionsince it addia bolting operation or to the action of a cyclone selectortionally results in a substantial reduction in the quantity for thepurpose of separating the finest particles from the of water which isevaporated in the spray-drier and conseid powder. quently a veryconsiderable economy in total consumption In all cases also, the powderwhich has been subjected of steam which is necessary for the entireprocess. to the secondary drying treatment can undergo a coolingWhatlclaim is: process, 1. Process for the production of milk-productpowders, The comparative table given below indicates b way of comprisingthe steps of providing a starting milk-product nonlimitative example theresults obtained in the producconcentrate containing a proportion of drymaterial which tion of a skimmed milk powder, on the one hand by isgreater than 45% and having a temperature which is means of aconventional spray-drying process and, on the greater than 45 C.,subjecting the starting milk-product other hand, by means of the processaccording to the inconcentrate to a spray-drying process by effectingthe vention by making use in both cases of different types drying withdrying air in the spray-drier until a powder of spraying devices. isobtained having a water content within the range of NORMAL TREATMENTWITHOUT REMOISTENING OF THE POWDER Pressure spraying nozzlesCompressedair spraying Centrifugal disc nozzles Conventional TreatmentConventional Treatment Conventional Treat ment;

spraying according spraying according spraying accordin treatment to thetreatment to the treatment to the invention invention inventiConcentration prior to spraying 43-44% 48 to 55%. -4 46 to 48%. 47% 50to 75%. Temperature of the concentrate a. 45 C 60 C 45 C 60 C 45 C 60 C.Intermediate moisture content of the 5.5%. 5.5%. 5.5%.

powder.

Final moisture content 3.5% -5%- 3 5% 35%. Commercial density 0.6. r..0.7 .6 0,... 0.7 5 Occluded air 15 cmfi/IOO g 8 emf/100 16 (bin 00 g 8 020 to 30 emfl/IOO g. Real solubility Good Very good"... Good Go d,

4.5 to 7%, and separating the powder from the drying In the applicationof the process according to the inair and then subjecting the powderthus obtained and havvention, it is possible in all cases to increasethe propor- 40 tions of dry material contained in the starting conceninga Water content within the range of 4.5 to 7% directly trate asindicated in the above table so as to bring them, to a differentsecondary drying process for a period of for example, above providedthat the evaporator tlme so as to reduce its water content toapproximately which is employed for the preparation of this concentrate3.5%. permits the possibility of obtaining such a degree of con- 2.Process for the production of milk-product powders centration in normalindustrial operation. It is in that as defined in claim 1, wherein thestarting milk-product case also necessary to increase the moisturecontent of the concentrate contains from 50 to 55% dry solids and is atpowder at the outlet of the spray-drier to approximately a temperaturewithin the range of to C. when it is 66.5%. r fed into the spray drier,and wherein the powder obtained Furthermore, as has been mentionedearlier, all the nufrom the spray-drying process has a water contentwithin merical values which have been specified in the foregoing therange of 4.5 to 6%. have been given in the case of skimmed milk.However, it 3. Process in accordance with claim 2, further includshouldbe made clear that the invention also applies to ing the Steps ofsubjecting the powder from the secondary the treatment of other milkproducts and in particular to p drying process to a separation operationso as to separate milk having a high fat content (whole milk or enrichedthe finest particles therefrom, and then reintroducing the milk) andresults in a similar improvement in the qualities separated fineparticles into the spray-drier. of the powders which are finallyobtained, although this last-mentioned application has higherconcentrations of References Clted Starting Concentrates- UNITED STATESPATENTS It must finally be understood that the present invention 60 21835,586 5/1958 Peebles 99 56 also includes withln its scope anyalternative form of ex- 2 934 434 M1960 H artman et a1. 99-56 ecutlon ofthe process described above, in WhlCh the 3 065 076 11/1962 W enner etal 99 203 X lncrease in concentration of the starting concentrate as a 3231 386 N19 Hutton et a1 99 203 X means for increasing the density ofthe final product is replaced by one or a number of other known meansfor FOREIGN PATENTS achieving the same result and which have beenmentioned 226,996 1/ 1959 Australia,

earlier (increase in the viscosity of the concentrate, reduction of thespeed of the spraying disc or of the pressure RAYMOND JONES, PrimaryExamine!- of the spraying nozzles, modification of the inlet tempera-HEYMAN, Assistant

